Micromachined devices include devices, such as actuators and motors, in which a movable element moves in a direction of motion with respect to another element. In some applications, the direction of motion is along a curved path, whereas in other applications the direction of motion is along a straight path. Such devices include a suspension that supports the movable element relative to the other element in a manner that allows the movable element to move freely in the direction of motion. Desirable properties of the suspension include that the suspension allow a broad range of movement in the direction of motion and that the suspension have a high compliance in the direction of motion. A suspension with a high compliance reduces the force that a motor needs to generate to move the movable element.
An electrostatic or electromagnetic motor used to move the movable element in the direction of motion not only generates a force in the direction of motion, but additionally generates parasitic forces with components in directions orthogonal to the direction of motion. More than minimal motion of the movable element in a direction orthogonal to the direction of motion is undesirable since it can result in physical contact between the movable element and the other element.
What is needed is a suspension for use in micromachined devices that has a high compliance in the direction of motion of the movable element, and that has a low compliance in at least one direction orthogonal to the direction of motion. The suspension should maintain a low compliance in the orthogonal direction over a substantial range of displacement of the movable element in the direction of motion. What is also needed is a suspension having a structure capable of easy fabrication using conventional micromachining techniques and that is reliable over many cycles of operation. Finally, what is needed is a suspension that can be configured to allow the movable element to move along either a straight path or a curved path.
The invention provides a pivot-less Watt linkage, a pivot-less Watt linkage-based suspension and a micromachined device. The pivot-less Watt linkage and the suspension incorporating the pivot-less Watt linkage has a high compliance in a direction of motion and a low compliance in at least one direction orthogonal to the direction of motion.
Specifically, the invention provides a pivot-less Watt linkage for supporting a first rigid element relative to a second rigid element to permit relative motion between the rigid elements. The pivot-less Watt linkage comprises an elongate, rigid, floating beam, an elongate first flexible beam, an elongate second flexible beam and a flexible member. The first flexible beam extends in a first direction from a first point on the floating beam to the first rigid element. The second flexible beam extends in a second direction, substantially opposite the first direction, from a second point on the floating beam to the first rigid element. The second point is spatially separated from the first point along the length of the floating beam. The flexible member extends in the first direction from a third point on the floating beam to the second rigid element. The third point is intermediate between the first point and the second point.
The motion is along a substantially straight path when the third point is substantially mid way between the first point and the second point. The motion is along a curved path when the third point is offset along the length of the floating beam from mid way between the first point and the second point, or when the flexible beams are of unequal length.
The flexible member may be a first flexible member, and the pivot-less Watt linkage may additionally comprise a second flexible member that extends in the second direction from a fourth point on the floating beam, opposite the third point, to the second rigid element.
The floating beam may have a compound structure including a first rigid beam section, a second rigid beam section, a third flexible beam and an additional flexible member. The first and second beam sections are each elongate. The first and third points are located in the first rigid beam section. The second point is located in the second rigid beam section. The third flexible beam extends from a fifth point on the first rigid beam section to a sixth point on the second rigid beam section. The fifth point is at a greater distance along the length of the first rigid beam section from the first point than the third point. The sixth point is spatially separated from the second point along the length of the second rigid beam section. The additional flexible member extends parallel to the second rigid beam section from a seventh point on the second beam section, remote from the second point, to the rigid element.
The floating beam, the flexible beams and the flexible member may be portions of a unitary structure. The unitary structure may constitute part of a single device layer. The pivot-less Watt linkage may include a major surface and the cross-sectional shape of the pivot-less Watt linkage in a plane parallel to the major surface may be independent of depth from the major surface.
The invention also provides a pivot-less Watt linkage-based suspension for supporting a first rigid element relative to a second rigid element to permit relative motion between the rigid elements. The suspension comprises pivot-less Watt linkages. Each pivot-less Watt linkage includes an elongate, rigid, floating beam, an elongate first flexible beam, an elongate second flexible beam and a flexible member. The first flexible beam extends in a first direction from a first point on the floating beam to the first rigid element. The second flexible beam extends in a second direction, substantially opposite the first direction, from a second point on the floating beam to the first rigid element. The second point is spatially separated from the first point along the length of the floating beam. The flexible member extends in the first direction from a third point on the floating beam to the second rigid element. The third point is intermediate between the first point and the second point.
Finally, the invention provides a micromachined device that comprises a first rigid element, a second rigid element and a pivot-less Watt linkage-based suspension for supporting the first rigid element relative to the second rigid element to permit relative motion between the rigid elements. The suspension includes pivot-less Watt linkages, each of which comprises an elongate, rigid, floating beam, an elongate first flexible beam, an elongate second flexible beam and a flexible member. The first flexible beam extends in a first direction from a first point on the floating beam to the first rigid element. The second flexible beam extends in a second direction, substantially opposite the first direction, from a second point on the floating beam to the first rigid element. The second point is spatially separated from the first point along the length of the floating beam. The flexible member extends in the first direction from a third point on the floating beam to the second rigid element. The third point is intermediate between the first point and the second point.
The pivot-less Watt linkage and the pivot-less Watt linkage-based suspension of the invention provide several advantages over conventional suspension elements and suspensions currently used in micromachined devices. The pivot-less Watt linkage and the pivot-less Watt linkage-based suspension allow the movable element to move in a direction of motion over a large range of movement. The motion may be along a straight path or a curved path. Additionally, the pivot-less Watt linkage and the pivot-less Watt linkage-based suspension maintain a low compliance in at least one direction orthogonal to the direction of motion as one of the rigid elements is displaced in the direction of motion from its rest position. Further, the pivot-less Watt linkage and the pivot-less Watt linkage-based suspension provide a high efficiency in terms of packing density.
Other features and advantages of the invention will become apparent to one of ordinary skill in the art from the following drawings and detailed description.